Mysterious Midcontinent Rift a Geological Hybrid

The Midwest's biggest geological feature, a mysterious Midcontinent Rift some billion years old, is actually a geological hybrid, according to new research.

The 1.1 billion-year-old Midcontinent Rift is an ancient and giant 2,000-mile-long underground crack that starts in Lake Superior and runs south to Oklahoma and to Alabama. Scientists have long wondered how this massive piece of scenery came to be, and now an international team of geologists has come up with an explanation - it's a geological hybrid.

Scientists from Northwestern University, the University of Illinois at Chicago (UIC), the University of Gottingen in Germany and the University of Oklahoma say that the rift evolved in three stages. It first started as an enormous narrow crack in the Earth's crust that eventually filled with an unusually large amount of volcanic rock, until the igneous rocks were forced to the surface, forming the beautiful scenery we see today.

"The Midcontinent Rift is a very strange beast," the study's lead author, Carol Stein, professor of Earth and Environmental Sciences at UIC, said in a statement. "Rifts are long, narrow cracks splitting the Earth's crust, with some volcanic rocks in them that rise to fill the cracks. Large igneous provinces, or LIPs, are huge pools of volcanic rocks poured out at the Earth's surface. The Midcontinent Rift is both of these - like a hybrid animal."

"Geologists call it a rift because it's long and narrow," explained co-author Seth Stein, "but it's got much more volcanic rock inside it than any other rift on a continent, so it's also a LIP. We've been wondering for a long time how this could have happened."

The researchers used in-depth images of the Earth to investigate the rift's rock layers, kind of like how an X-ray can view our bones.

Stein is now are working with other geologists to help park rangers and teachers tell this story to the public.